<button onClick="toggleParallel()">toggle Parallel projection: <i class="text">(off)</i></button>
 <tr>
        <td><b>Clip Plane 1</b></td>
        <tr>        
          <td>
            Position
            <input class='plane1Position' type="range" min="-200" max="200" step="1" value="0" />
          </td>
        </tr>
    </tr>
    <tr>
        <td><b>Clip Plane 2</b></td>
        <tr>        
          <td>
            Position
            <input class='plane2Position' type="range" min="-200" max="200.0" step="1" value="0" />
          </td>
        </tr>
    </tr>
